Chronic polymyositis: presence of coxsackievirus A9 antigen in muscle.

We report a case of chronic recurrent polymyositis associated with increasing antibody titers of coxsackievirus A9 in serum during clinical exacerbations. Muscle biopsy specimens showed pathologic changes consistent with chronic myositis, including perivascular mononuclear cell infiltration and hyalinization of muscle fibers with cytoplasmic vacuolations. The specific fluorescence was observed in the muscle fibers stained with antiserum for coxsackievirus A9. These findings indicate that this viral subtype as the etiologic agent in this case and virus plays a pathogenic role in some cases of chronic polymyositis.